1. Field of the Invention
The present invention relates to an antenna unit and radio base station provided with that antenna unit.
2. Related Art Statement
Recently, demand for the cellular mobile phone of the CDMA (Code Division Multiple Access) system is increasing, and with that, techniques of coping with traffic increase are attracting attention. One is the technique of adaptive array antenna. In this technique, a radiation pattern of an antenna is controlled to follow each of multi paths through which a user signal arrives so as to moderate interference by signals of other users.
There exists a technique in which the control of the radiation pattern of an array antenna is carried out in the baseband.
However, a signal subjected to the array antenna controlling in the baseband must passes through various circuits and cables before transmission from the antenna, and accordingly, when the signal arrives at each antenna, deviation due to distortion is generated between signals arriving at respective antennas. Thus, when there is deviation between signals arriving at respective antennas, it is impossible to transmit the signal with a desired radiation pattern.
Thus, a baseband processing circuit requires circuits for estimating level deviation and phase deviation generated in a radio frequency unit and cables and for compensating those deviations. Further, when cable length is large, it expands and contracts owing to variation in temperature, and accordingly, as a compensation circuit, use of an adaptive processing circuit is required.
In the present invention, a probe signal is applied to cables and a radio frequency unit, and an adaptive processing circuit uses this probe signal to perform the above-mentioned compensation.